November 2011 Build. Replaced battery at 46k. The positive post was actually cracked wide open and leaking acid everywhere. No clue how it happened, haven't touched the battery since I bought it from carmax at 32k miles. I suspect it was broken then but since I didn't notice I got screwed. Carmax only offers 30 days on the battery, extended warranty be damned.

^You turn you computer (the one you post from) off for a week, disconnect all power to it.
You come back and the date/time is still correct and all your setting are still there.

The automotive ECU/PCM is no different.
This business of disconnecting the battery resetting things is a partial untruth. For a good many things there's a mental aspect that changes and not a running condition. And since virtually no one has hard data that removing power changes anything, it's opinion that shouldn't be trusted.

Basically (very) what 'resetting the computer' does is it clears the learned data from when a problem is sensed.
So let's say the MAF is not reading correct (the computer thinks), from the time that data is sensed to when the computer is reset will be cleared. Which means that if the MAF has not been repaired, the same data will be learned.

If there is no problem sensed, no data is lost. That would include driving habits. If there are no fault codes, nothing is lost.

I'm pretty darn sure it's written in the manual that the PCM / TCM will once again go through the relearning procedure after a battery failure.

January 2014 purchase of a 2012 Focus. Battery is Ford and looks original. Hard starting in the morning sometimes if cold temperatures are combined with a short trip or two the night before. If I drive to my parents house and back, a roughly 40 minute round trip, it has no problems. But if I drive to the corner store and back, it will usually hard start in the morning, especially if it's well below freezing.

I'm also used to the factory battery lasting 5+ years and even the cheapest of the cheap aftermarket batteries lasting 3-4. But I do know that my car sat on the lot for at least a few months before I got it, and who knows if it was ever driven or even moved. Batteries don't take well to sitting for long periods, especially in newer cars which tend to have more than just the clock pulling power while the car is parked.

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